PEPPERMINT LEAF SPOTS

Abstract

Objective. To establish the symptomatology of the manifestation, distribution and development of leaf spots on peppermint varieties of different resistance in different phases of plant vegetation. Methods. The experiments were carried out during 2021-2023 in the conditions of the educational and scientific laboratory “Demonstration Collection Field of Agricultural Crops” of the NULES of Ukraine, on mint varieties: Posulska linaloolna and Chernolista. The records were carried out during the growing season of the crop before the first and second slopes. During the phytopathological evaluation of affected plants, the intensity of the disease was determined by spotting, setting the point of damage of the selected peppermint samples on a 5-point scale. The number of affected plants and the degree of damage were determined by the area of the affected surface of the organs and the intensity of manifestation of other signs of the disease in percentages given in the scale and were calculated according to the formulas for the spread and development of the disease. Results. Spots are one of the most common diseases of plants, including medicinal crops. These diseases affect the leaf plate of the plant, cause a hypersensitivity reaction, forming zones of dead plant tissue, thereby disrupting physiological processes, affecting photosynthesis, respiration, and transpiration. As a result, they lead to a deterioration in the quality of medicinal raw materials and reduce their quantity. During the experiments, we discovered necrotic leaf diseases: anthracnose (causing agent – Sphalocema menthae) and alternariosis (causing agent – Alternaria menthae) of peppermint. Anthracnose is a dangerous fungal disease that affects many different crops, including Mentha spp. It appears on the vegetative part of the plant in the form of round, oval or irregularly shaped, brown, black or dark spots with a white center, up to 5 mm in diameter. These spots darken as they grow and can also expand to cover the entire leaf blade. The causative agent overwinters on plant remains in the form of conidia or mycelium. The development of anthracnose is facilitated by a large amount of precipitation, high relative humidity at moderate and high temperatures. Alternaria of peppermint was detected during research as a brown or black spot, in the place of which the plant tissue gradually dies. Just like the causative agent of anthracnose, the source of Alternaria infection is stored on plant remains in the form of conidia or mycelium. Anthracnose reached its maximum development in 2023 at the beginning of flowering and was: the spread of the disease on the Blackleaf variety 60.3% and on the Posulska linaloolna variety 43.3% with the development of the disease 18.3% and 11.5%, respectively. Alternaria had the same tendency, it was most manifested in 2023 on the Chernolista variety, distribution – 68.0% and development – 19.7%, on the Posulska linalool variety, distribution and development were 49.7% and 13.6%, respectively. When conducting records of damage to peppermint by anthracnose when the plant grows on the second cutting, based on the results of three-year data, we noted an increase in the indicators of the spread and development of the disease from 2021. by 2023, on the Chernolista variety, the spread is from 16.3% to 36.7% and the development is from 3.5% to 11.7%. On the Posulska variety, linalool distribution is from 13.2% to 28.6%; development from 4.8% to 8.2%. Conclusions. When studying the development and distribution of peppermint spots, we can say that on the Posulska variety, linalool leaf spots have a somewhat smaller development and distribution, and they also appear in later phases of plant vegetation than on the Chernolista variety. This is related to the morphological and physiological features of plants, which require additional research. According to the results of three-year studies, an increase in the prevalence and development of anthracnose and alternariosis of peppermint has almost doubled, which is associated with the accumulation of the source of infection, and requires disease monitoring and protective measures to reduce the accumulation of pathogens.